Currently, mobile communication service technology can be classified into an asynchronous service environment in Europe and a synchronous service environment in North America. Further, as standards of new mobile communication technology for transmitting packets at high speed, International Mobile Telecommunications (IMT)-2000 service has been developed around North America and Europe.
The synchronous IMT-2000 type of service has been developed into Code Division Multiple Access (CDMA) 2000 1x or CDMA 2000 1x Evolution Data Only (EV-DO), and the asynchronous IMT-2000 type of service has been developed into Wideband CDMA (WCDMA) Universal Mobile Telecommunications System (UMTS) service. In such a service environment a roaming problem between synchronous and asynchronous networks has been raised as the greatest outstanding problem. Accordingly, a terminal supporting dual band/dual mode to enable stable roaming between synchronous and asynchronous mobile communication networks is required.